This invention relates to digital techniques used in providing pixels for refreshing a display screen.
A still picture on a television or computer monitor""s display screen appears, through human eyes, to be fixed in color and location. However, due to technical requirements of the display screen, the picture must be repeatedly redrawn or xe2x80x9crefreshedxe2x80x9d several tens of times each second so as to prevent the picture from being distorted. The higher the refresh rate, the more pleasing and accurate the picture appears and the less strain its viewing presents to the eyes, particularly when displaying motion pictures, i.e. video. For instance, if video is being displayed at 24 frames or pictures per second, a refresh rate of 100 Hz may be acceptable.
A computer monitor receives display information, including the picture elements or xe2x80x9cpixelsxe2x80x9d that define each frame of video to be displayed, from a computer system video adapter. Digital computer monitors, as contrasted with analog monitors, have a digital interface to the video adapter. That is, the input signal which contains the pixels received from the video adapter is digital rather than analog. There are certain advantages to such a scheme, including the use of a general purpose digital peripheral bus rather than a dedicated analog link.
A serious bandwidth problem arises, however, when attempting to provide high refresh rates in digital monitors that also have high resolution. For instance, a 100 Hz monitor allowing a high resolution of 1280xc3x971024 pixels in each frame must be continuously provided with 1280*1024*100xcx9c131 million pixels per second. With each pixel being, for instance, three bytes long, this translates to an unacceptably high data transfer rate from the video adapter to the digital monitor of approximately 400 megabytes per second.